Attributes:

SPEI [-] (element wise)

KSPE [-] (node wise) (only for calculations with the INSTAT module)

For horizontal models:

For transient calculations in unconfined aquifers, a storage coefficient S [-] can be assigned to each element (SPEI) or each node (KSPE). For confined aquifers, the default specific storage coefficient S0 = S / thickness = 3.3 10^-6 is used instead of the SPEI or KSPE values. This preset value can be changed for the SITRA module via the sitr file.

For 3D models and vertical models:

Normally, the transient pressure equation () is used to calculate the specific storage coefficient:

Transient pressure equation

the porosity value specified with the PORO attribute is used for the value n [-]. If SPEI or KSPE is specified, the porosity value is replaced by that value, otherwise the default porosity value of 0.2 is used.

For transient flow calculations , the user is required to select which calculation module should be used. The SITRA module uses the element-wise storage coefficient SPEI or the porosity via the attribute PORO. The INSTAT module also utilizes element-wise values for the storage coefficients or porosity. Input via SPEI is thus preferable, however, it is also possible to use the node-wise KSPE value for the INSTAT module.